TABLE 2.

¹³C NMR data of premithramycins A1 to A4 at 125.7 MHz in d₆-acetone^a

Position	A1	A2	A3	A4
C-1	NOb	195.5 sc	196.2 sc	202.4 s
C-2	113.1 s	113.3 s	113.2 s	75.9 dc
C-3	NOb	189.5 sc	189.0 sc	41.9 d
C-4	78.5 d	78.3 d	78.0 d	26.4 t
C-4a	43.0 d	43.1 d	43.0 d	135.3 s
4-OCH3	61.1 q	61.1 q	61.4 q
C-5	26.6 t	26.6 t	26.6 t	101.0 d
C-5a	136.2 s	134.8 s	134.6 s
C-6	117.9 d	117.9 d	117.8 d	160.0 s
C-6a	142.8 s	140.3 s	140.1 s
C-7	103.2 d	102.8 d	102.8 d	109.0 s
7-CH3				6.8 q
C-8	160.8 sc	162.2 s	162.1 s	155.8 s
C-8a				105.9 s
C-9	102.2 d	110.8 s	110.7 s	NOb
C-9a				106.9 s
9-CH3		8.2 q	8.2 q
C-10	163.3 sc	157.7 s	157.5 s	115.2 d
C-10a	107.8 s	107.3 s	107.1 s	138.5 s
C-11	168.0 s	168.1 s	168.0 s
C-11a	108.3 s	108.3 s	108.0 s
C-12	NOb	193.1 sc	193.0 sc
C-12a	85.5 s	85.5 s	85.5 s
C-1′	204.1 s	204.3 s	204.3 s	81.0 dd
1′-OCH3				57.7 q
C-2′	28.2 q	28.4 q	28.4 q	210.3 s
C-3′				78.1 de
C-4′				67.4 de
C-5′				18.7 q
C-1A	98.2 d	98.3 d	98.3 dd	100.0 d
C-2A	40.5 t	38.6 t	38.5 t	37.0 t
C-3A	71.9 d	82.0 d	81.9 d	80.9 dd
C-4A	77.9 d	75.7 d	75.6 d	74.4 d
C-5A	72.9 d	72.9 d	72.8 d	71.6 d
C-6A	18.2 q	18.4 q	18.5 q	17.1 q
C-1B		100.7 d	100.5 d	99.4 d
C-2B		35.6 t	32.8 t	31.6 t
C-3B		69.3 d	77.1 d	75.9 d
C-4B		70.6 d	69.2 d	67.9 d
C-5B		71.7 d	71.2 d	70.0 df
C-6B		16.9 q	16.9 q	15.6 q
C-1C			98.2 dd	97.0 d
C-2C			44.6 t	43.4 t
C-3C			71.1 s	69.7 s
3C-CH3			27.7 q	26.1 q
C-4C			77.1 d	75.8 dc
C-5C			71.3 d	70.1 df
C-6C			18.7 q	17.4 q

^aδ in parts per million relative to internal trimethylsilyl. Multiplicities and assignments are from the APT, hetero-multiple quantum correlation, and HMBC experiments. 

^bNO, not observed due to tautomerization. 

^cto f Assignments are interchangeable pairwise.